Extraction of tin from ores



' Oct. 24, 1933.

L. A, WOOD ET AL EXTRACTION OF' TIN FROM ORES Filed Aug. 8, 1932AGGOMERATES- W4 TER.

Patented Oct. 24, 1933 l f 1,931,944

UNITED STA-TES, PATENT OFFICE EXTRACTION Vor TIN. FRoM'oREs Louis AlbertWood and Henry Livingstone SulmanrLondon`,jEngland' I Appli-cationvAugust s, .-1932, serial N.` 627,944,

' Yandin Great Britain June 15511932 1o claims. (ci. 23a-9s) Thisinvention comprises improvements in o1' A desirable'proportion of'calcium chloride relating to the extraction of tin from oresrin-(reckoned'as 100% CaClz) is roughly about one cluding under that termconcentrates 4and the androne-half times the theoretical quantityindilike. The invention relates to processes of the cated bythe equationy 60 5 type in which tin-bearingores mixed with carbo- Y Y naceousmatter are heated inthe presence of a S1102+C+CaC12=CaO+COI`SnC12halogen salt out of substantial Contact with air Thus an ore carrying4%0f tin will require so as to form stannous chlordevwhichV vdistilleabout 6% CaCl2. In our trials on basic ferrugifrom the ores and iscondensed. y nous cassiterite ores carrying 4.3% Sn, 'Z1/2% of '10According to the present invention a process 90% CaClz has commonly beenused, and for-7.7% 65 for the extraction of tin from ores bychloridiza-` Sn ore, 13% of thisfsalt.- tion in the presence of carbonis characterized The total quantity of carbon should be in excess bythefact that the chloridizing agent consists of 'that required to reduceall metals present to of calcium chloride solution admixed .with the themetallic state and it is found that this quan- 15 ore, which solutionacts as a binder to prevent tity of carbon eliminates any tendency tofusion 0 dusting of the charge. It has been found that or incipientfusion in the course of the process. calcium chloride solution, althoughgiving up its The damp sandy mixture is then introduced Water ofhydration gradually while it is heated, into a suitable drier 16 lsuchas a rotating inclined acts as a very effective binding agent to holdtubular furnace heated by the waste gases 17 from 20 together the orewith which it is mixed and prethe furnace hereinabove referred to. Inthe dry' 75 vent losses Aby dusting in the furnace, because at ingfurnace the material tends to agglomerate the lower temperatures *itr isliquid through the into small aggregates, which are held together bypresence of water and at the higher temperathe calcium chloride as abinder and which are, 'iures it is liquid through being fused. ltherefore, not liable to produce undue quantities Preferably the ore andcarbon are mixed or of dust.V From the drier the mixture is fed'toground together in admixture with a calcium the hearth of the furnace18.v chloride solution to the form of damp or wet The furnace 18 ismulTle-heated, for example sand. The wet mixture may be introduced intoby producer gases, introduced at burner 19, and a drying chamber andtherein heated to such a in it the ore-mixturev is raised to atemperature temperature as to remove excess water while beof the orderof 800 to 900 C. It is'found that 8 ingagitated to form agglomerateswhich are not all tendency to"fritting`, that is fusion or in liable toproduce dust whenv subsequently heated cipient fusion of the materialwhen raised to this to the're'action temperature. high temperature inthe furnace 18, is obviated The process can, in View of the fact thatthe by the presence of va suitable quantity of carbon material is notliable to produce undue quantities as hereinabove described. The hearthor hearths of dust, be carried out readily as a continuous areoperatedby the usual rabbles for causing ore process in a mulile furnaceof the type through to travel gradually through the furnace. Stanwhichthe ore is worked continuously by moving nous chloride is evolved anddrawn off at 20 and parts of the furnace itself. condensed in condenser21. There is an outlet 2'7 40 The invention will now be described Withreferfor ore residues. n 95 ence to the accompanying drawing, which con-It is important to prevent contact between stitutes a diagrammatic iiowsheetr showing one metallic iron components of the apparatus and form ofprocess according to the' invention by stannous chloride condensations.That is to say, way of example. such iron 'components must be kept at atem- Tin ore is fed through a crushing plant diaperature abovethevolatiliz'ation point of tin chlo-' grammatically indica' ed at 1-1, theplant being Tide- In the body 0f the furnace 18 itself, WhereA such thatthe product will pass a screen having the temperature is above thedistillation temperaabout four meshes to the lineal inch. lThe ore tureof stannous chloride, the employment of iron is then introduced into agrinder 12 shown as iS Permissible Inl/he condensing DOIOn 0f the beingof the roller-and-pan type having a pan 12 apparatus, however, it isYpreferable that fused 105 and rollers 13; From a hopper 14 carbonaceousSilica be emplOyed in the hotter DOIlOnS and material such as crushedcoal isv also fed into the enamelled or other. vitreous material in thecooler grinder 12 and the whole is moistened by calcium portions.chloride solution 15. The mixture is ground to- The furnace and thecondensing apparatus are gether to the consistency of Wet sand.maintained at a pressure below that existing out- 110 side the muiehearth, conveniently, by means of an exhaust fan 22, so that alltendency of stannous chloride to leak outwardly is avoided. Thisprecaution is particularly beneiicial because any vapours which mightleak through cracks in the apparatus would in practice be lost.Moreover, if any of the retort materials. are of. a pervious character aminuspressure outside the hearth chamber tends to prevent absorption ofstannous chloride vapours thereby.

Due to its high vapour density and high boiling point, stannous chloridereadily condenses to the liquid form, i. e. at 606 C. and thereforecollect in quantity in any leading-out tube such as 20 which falls belowthis temperature. It is therefore advisable to avoid long horizontallengths of piping and even'V sloping. tubes or pipes must be kept at atemperature above the solidifying point of stannous chloride, viz. 250C.

The condenser 21 may consist of a chamber with non-peryious walls,fitted. with water-spray 2i or steam inlets, to dissolve thestannouschloride.- which collects asa solutionZB. It is followed by ascrubbing tower 25 in which the nal traces of tin chloride suspended inthe permanent gases, are arrested. The effluent' scrubbed gases 2.6consist largely of carbon monoxide and can be used for supplying the gasburners 19- in the. munie-heated furnace.

The ore residues discharged from the furnace 18 at 27 are taken to aleaching vplant 28 andv leached with water 29 which effects asubstantial recovery of excess calcium chloride and the calcium chloridesolution thus produced is led, as

5 shown at 30,. to join the calcium chloride solution supplyV l5 for usein the grinderll l The stannous' chloride solution recovered from thecondenser 21 and scrubber 25 is delivered to a filter 31 and the clearfiltered solution is taken to electrolytic apparatus 32 where crystalsof pure tin are obtained at the cathode and. chlorine gas at the anode.Thechlorine gasis collected and passed through a tower 33 packed withlimestone and. wetted with water 34, vAs a result calcium chloride:solution 35 is recovered andv led back as shown at 15 to the ginder- 12.Additional calcium chloride solution beyond that supplied at 3v()v and35 can be added at 36 for make-up purposes.

insteadl of recovering the tin by electrolysis stannous chloridecrystals. can be recovered from theeiiluent iilter 31 b-y evaporation.Instead of leading the chlorine gas into a tower 33 packed with lime itcan be mixed with a hydrogenous reducing gas, such as coal gas, watergas or producer gas,y and the mixture canbe passed through a zone packedwith a contact agent, suchas firebrick heated to redness. As` aconsequence hydrochloric acid. is formed and can be condensed in waterso that the whole of the chlorine may be recovered. as hydrochloricacid.

1. A process for theextraction of tin from ores comprising incombination the steps of admixing the ore with carbonaceous .materialand calcium chloride solution, whereby the calcium chloride solutionacts as a chloridizing agent and also as a binder, and thereafterheating the mixture to eiiect distillation of the tin as chloride.

A process for the extraction of tin from ores comprising in combinationthe steps of admixing the ore with carbonaceousv material and calciumAchloride solution to the form of damp or wet sand and thereafterheating the mixture to distil the tin therefrom as chloride.

3. A process for the extraction of tin from ores comprising incombination the steps of admixing the ore with carbonaceous material andcalcium chloride solution to the form oi damp or wet sand, drying themixture to remove free water and thereafter heating' the mixture: todistil the tin therefrom as chloride.

4. A process for the extraction of tin from ores comprising inlcombination the steps of admixing the ore with carbonaceous material andcalcium chloride solution to the form of damp or wet sand, granulatingthe mixture byV drying it to the point of removal of free water whileeffecting agitation to form agglomerated masses,

and thereafter heating the mixture to distil the tin therefrom aschloride.

5. A process for the extraction of tin from ores comprising incombination the steps of admixing thel ore with carhonaceous materialand calcium chloride solution to the form of damp or Wet. sand,introducing the mixture into ay rotatable drying chamber so as to formagglomerated dry masses by rolling and to remove free water andthereafter heating the mixture to distil the tin therefrom as chloride.

6. A process for the extraction of tin from ores comprising incombination the steps oi'. admixing the ore with carbonaceous materialand calcium chloride solution whereby the calcium chloride solution actsas a chloridizing agent and also as a binder, and thereafter heating themixture in a munie-heated hearth tov effect distillation of the tin aschloride.

7. A process for the extraction of tin from ores comprising incombination the steps of adrnixi'ng the ore with carbonaceous materialand calcium chloride solution whereby the calcium lll) chloride solutionacts as a chloridizing agent L and also as a binder, and thereafterheating the ores comprising in combination the steps of ad- -ff mixingthe ore with carbonaceous material and calcium chloride solution to theform of` damp or wet sand and thereafter heating the mixture in amunie-heated hearth while rabbling to distill the tin therefrom aschloride.

9'. A process for the extraction of tin from ores comprising incombination the steps of admixing the ore with carbonaceous material andcalcium chloride solution to the form of damp or Wet sand, granulatingthe mixture by dryingY it to the point of removal of free water whileeffecting agitation to form agglomerated masses and thereafter heatingthev mixture in a Inutile heated hearth while rabbling it, to distillthe tin therefrom as chloride.

10. A process for the extraction of tin from Q ores comprising incombination the steps of admixing the ore with carbonaceous materialvand calcium chloride solution to the form of 'damp or Wet sand,introducing the mixture into a roj i tatable drying chamber so as toformagglomerated dry masses by rolling and to remove free water, andthereafter heating the mixture in a munie-heated hearth while .rabblingit, to distill the tin therefrom as chloride.

LOUIS ALBERT WOOD. HENRY LIVINGSTONE SULMAN.

